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  3. The crustaceans known as harpacticoids are very widespread in marine sedimen

The crustaceans known as harpacticoids are very widespread in marine sedimen

游客2024-01-10  44
问题     The crustaceans known as harpacticoids are very widespread in marine sediments, where they feed on microorganisms by ingesting the sediment particles to which the microorganisms adhere. Heavy metals, such as those found in industrial pollution, readily adhere to sediment particles. Harpacticoids are poisoned by heavy metals but are unaffected by most other pollutants. Therefore the concentration of harpacticoids in an area is a good indication of whether that marine environment contains heavy metals.
    Which of the following is an assumption on which the argument relies?
选项 A、Industrial pollution is the principal source of heavy metals in marine sediments.
B、Harpacticoids are the only crustaceans that feed on microorganisms by ingesting sediment particles.
C、Harpacticoids are more susceptible to poisoning by heavy metals than are other marine organisms.
D、The microorganisms that harpacticoids feed on are not killed by pollutants that are harmless to harpacticoids.
E、The microorganisms that harpacticoids feed on absorb heavy metals.
答案 D
解析 选项取反。微生物被对猛水蚤无害的污染物杀掉→因为没有微生物可吃，所以有无害污染物的区域依然没有猛水蚤。而原文想得到的结论应该是没有猛水蚤就等于有重金属。但是该选项取反之后，没有猛水蚤还可以表明这个地方没有无害污染物，这使得猛水蚤不能成为可靠的判断重金属的指标，推翻原文，D正确。A项本题和重金属的来源无关。B项选项取反。猛水蚤不是唯一一种通过吃沉积物颗粒来吃微生物的甲壳类动物一猛水蚤依然是以这种方式吃微生物的甲壳类动物，没有推翻原文。C项本题关键不在于对比猛水蚤相比于其他生物对重金属的敏感度。我们只关心猛水蚤本身的敏感度。E项微生物吸收重金属对我们判断文章结论没有帮助。
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